Robert Hayes, pictured here during his trial, pleaded guilty to the murder of Petra Rohrbaugh, 52, in her Old Bridge home in 2010.Patti Spaone/The Star Ledger

NEW BRUNSWICK — Robert Hayes sat in the jury box, his hands shackled in front of him, answering questions from his attorney.

In a strong voice, but without a trace of emotion today in Superior Court in Middlesex County, Hayes, 36, recounted how he broke into Petra Rohrbaugh’s house in Old Bridge in April 2010 "to kill her."

Hayes, who interrupted his murder trial to plead guilty to murder and other charges, told Judge Michael Toto that once he was in the Hilltop Boulevard home, he went to the master bedroom, found the 52-year-old woman and "strangled her until she was dead."

He then set the bed on fire, he said, "in order to burn down the house."

As Hayes detailed how he killed Rohrbaugh, her daughter, Annika Werner, sitting in the front row of the courtroom, started to sob.

Hayes faced life in prison had he been convicted of murder, and would have had to serve 85 percent of his sentence.

As part of his plea agreement, the state will recommend that Hayes receive 30 years without parole when he is sentenced on April 21.

Werner, who found her mother’s body the morning of April 8, 2010, after Rohrbaugh had not answered repeated phone calls that began the day before, said that sentence was not enough.

"Thirty years is not enough to make up for the remainder of her life that she lost," the nurse and mother of two young children said. "But I’ll accept that. It’s some closure."

Werner and others testified that Hayes stayed in the house next to Rohrbaugh’s and struck up a friendship with the music teacher, who just months before had moved from Maryland to be closer to her daughter and family.

Sometime in early 2010, Hayes began pressuring Rohrbaugh for a sexual relationship. Rohrbaugh refused, telling Hayes she was "married to God," according to witnesses at the trial.

Rohrbaugh was sufficiently upset about Hayes’ advances to complain to her daughter, son-in-law and neighbors, according to their testimony. One neighbor, Vincent Petzko, told the jury earlier this week that he and other neighbors confronted Hayes several weeks before Rohrbaugh’s death and told him to leave her alone — to just say "hi" and "bye" to her.

An autopsy showed Rohrbaugh was gagged, beaten and, with her hands tied behind her back, strangled before she was set on fire about 36 hours before her body was found.

In addition to murder, Hayes pleaded guilty to burglary, aggravated arson and desecration of human remains.

The state will ask the judge to dismiss aggravated sexual assault and two hindering charges at the time of sentencing.